* glom/libglom/connectionpool_backends/postgres.[h|cc]:
get_path_to_postgres_executable(): Return the already-quoted path
to avoid the need for manual quoting by the caller.
However, make this optional (but the default) so that the check in
* main.cc: can still work.
* glom/libglom/connectionpool_backends/postgres_self.cc: Use
Glib::shell_quote() instead of manually adding quote characters.
Hopefully this also escapes special characters, though we should try to
test this somehow.